The present invention relates to plants belonging to a novel Manilagrass variety newly produced by adding a genetic variation to a single line (strain) of Zoysia matrella (common name: Manilagrass) without conventional crossbreeding, cell fusion, gene introduction or the like, which variety retains the characteristics of conventional Manilagrass while also exhibiting a completely new character. Specifically, it relates to a novel Manilagrass that retains its green leaves under the same seasonal conditions in which conventional Manilagrass loses its green leaves. The present invention further relates to Manilagrass that retains its green leaves in winter while producing substantially no anthocyanins under normal cultivating conditions, Manilagrass that has a high stolon density, dwarfed Manilagrass, and newly invented Eragrostoideae plant developed using genotypes absent in conventional Manilagrass lines but present in Manilagrass of the invention.
xe2x80x9cManilagrassxe2x80x9d according to the present invention refers to Zoysia matrella that exhibits creeping properties by vegetative growth, having a blade width of 1.0-3.5 mm, and it does not include interspecies hybrid lines obtained by artificial crossbreeding with other species such as Zoysia japonica, Zoysia tenuifolia and Cynodon dactylon (see Fukuoka, H., xe2x80x9cTurfgrass and Its varietiesxe2x80x9d, ed. by Asano, Y. and Aoki, K., Jun. 15, 1998, Softscience Publications, pp.122-123).
Zoysia matrella (common name: Manilagrass) is widely used as a ground cover for a broad range of purposes, because of its many features including aesthetic appearance, ground spread, management ease, wear resistance, water stress resistance, growing power and creeping properties.
However, Manilagrass has certain disadvantages including withered leaf during winter, strong preferential growth of main apical buds, impaired appearance due to anthocyanins, and the need for more frequent trimming in summer due to intensified growth; for these reasons, it not only fails to satisfy market needs but is also limited in its uses.
Specifically, for uses that place importance on aesthetic appearance, for example, sports turfs, open areas such as parks, factory lawns and facility exteriors, rooftop heat-insulating greenery, gardens and the like, withered leaf during winter notably lowers the value of Manilagrass, and the concept of xe2x80x9cevergreen Manilagrassxe2x80x9d has been a requirement for numerous purposes and would meet a very strong market demand.
In order to compensate for withered leaf in winter of Manilagrass and Bermudagrass (Cynodon dactylon), many sports turfs are managed with the overseed method (a method in which Western grass, which is a cool season turfgrass, is sown over Manilagrass areas or Bermudagrass areas at the beginning of autumn in order to maintain the green appearance in winter, and then the western grass is killed off in spring to allow resprouting of the Manilagrass or Bermudagrass), or the withered leaf coloring method (a method in which the withered leaves of Manilagrass are colored with a green pigment or dye). These methods, however, require expensive investment each year leading to notable cost increase and, although they are often employed at golf courses and other sports turfs they are difficult to carry out in practice in most other fields, while the overseeding method also results in yearly weakening of the Manilagrass itself.
Withered leaf in winter of Manilagrass is also a fatal drawback for rooftop heat-insulating greenery, used for its effectiveness toward energy reduction and carbon dioxide gas fixation.
Withered leaf in winter of Manilagrass and Bermudagrass tends to result in bare ground due to the wearing that occurs with trampling, etc., and a further drawback, in the case of Manilagrass, is its susceptibility to winter weeds and spring sprouting weeds, which tend to promote turfgrass decay.
In addition to physical methods such as the overseed method and the withered leaf coloring method, the following measures have also been adopted to shorten the withered leaf in winter period of Eragrostoideae turfgrass.
(a) Dispersion of iron chemicals: Iron absorption promotes chlorophyll synthesis to increase the greenness of the plants.
(b) Dispersion of nitrogen fertilizers: This method is effective for maintaining greenness during the initial winter period but it also delays sprouting in spring, and because the withered leaf in winter period is not significantly shortened it is not a preferred method.
(c) Dispersion of 5-aminolevulinic acid (ALA): This has been reported to have a chlorophyll-increasing effect (xe2x80x9c5-Aminolevulinic Acid: Applications for Microbe Production and Lawngrassxe2x80x9d, Hotta, Y., Tanaka, T., Watanabe, K., Takeuchi, Y., Konnai, M., xe2x80x9cLawngrass Researchxe2x80x9d meeting journal, No.27, 1998, pp.138-139).
(d) Breeding methods: It has been attempted to crossbreed Zoysia matrella and Zoysia japonica, for example, to solve the problem of withered leaf in winter. Further collection and selection of regional lines throughout the world have also been attempted in order to obtain varieties with favorable genotypes, for example, by selection of lines with minimal withered leaf in winter. (For example, Fukuoka, H., xe2x80x9cTurfgrass and Its Varietiesxe2x80x9d, ed. by Asano, Y. and Aoki, K., Softscience Publications, Chap. 3, 3-2, pp.126-130). However, crossbreeding Zoysia matrella with other varieties tends to lessen the features of Manilagrass, with the resulting varieties having wider blade widths and inferior aesthetic appearance compared to Zoysia matrella, while the problem of withered leaf in winter is not satisfactorily solved. On the other hand, methods involving the latter collection of lines mentioned above have to date failed to provide Manilagrass with sufficient greenness in winter.
The present invention relates to Manilagrass characterized by retaining its green leaves under a condition where the mean temperature of a period of ten days is 6xc2x0 C. or below and the lowest temperature in this period is xe2x88x921xc2x0 C. or below, but not less than xe2x88x9215xc2x0 C., and by containing substantially no anthocyanins throughout the year.
The invention further relates to the aforementioned Manilagrass, characterized in that the length of the internode of a main stolon except the immature intemodes of the front part of the main stolon, which extends when attached to the soil surface under obstacle-free growth conditions, is about 0.9xe2x80x94about 0.6, where 1.0 is defined as the length for conventional Tottori Z. matrella (Tottori Sod Producers Association: the representative Manilagrass single line produced and marketed at 558-1 Oaza-Tokuman, Tohaku-cho, Tohaku-gun; Tottori, Japan).
The invention still further relates to each aforementioned Manilagrass, characterized in that the ratio of the main stolon length to the total lateral stolon length, measuring the total length of lateral stolons developing from the main stolon based on a main stolon length corresponding to at least 20 nodes from the tip of the main stolon of the turigrass of the invention, in stolons extending under obstacle-free growth conditions when attached to the soil surface, is at least 1.2 times compared to conventional Tottori Z. matrella. 
The invention still further relates to Eragrostoideae plant bred from any of the aforementioned Manilagrass as the parental strain by crossbreeding, mutation, cell fusion or gene introduction, that inherits any of the aforementioned characteristics.
The novel Manilagrass of the invention has notably higher lateral stolon extendibility compared to the parental strain (Tottori Z. matrella) or Japanese lawngrass (Zoysia japonica), and thus has a higher stolon density, forms a stratified mesh mat earlier and has much higher value for practical use.
Formation of a stratified mesh mat offers the following merits:
(1) Because growth (vegetative propagation) of Manilagrass by seed is difficult in practice, productivity can be improved as the method adopted is to strip a 1-2 cm upper layer, as harvest, each year from the production farm, and repopulate the grass from the remaining mat for harvest the following year;
(2) It is resistant to wearing;
(3) It can be rapidly reproduced even when the upper layer portion has been cut away (for example, as golf course divots);
(4) It increases cushioning properties for sports turf;
(5) It improves drying resistance properties (water retention, water absorption, water storage in plant body);
(6) It greatly improves the spread essential for slopes, riverbeds, etc., and thus helps protect surface soil layers;
(7) It is dense and gives attractive lawn tops;
(8) It can reduce weeds by the formation of dense turfs.
In addition, conventional Manilagrass produces anthocyanins and colors in the stems throughout the year and undergoes coloration, while anthocyanins are produced resulting in coloration even in the few living leaves remaining under daily mean temperatures of lower than about 10xc2x0 C., such that it presents a purplish red, dark green-purple or blackish-purple color, thereby losing much of its attractive green appearance. According to the present invention, however, the aforementioned problem is solved by providing the first variety of Manilagrass to contain substantially no anthocyanins.
In order to ensure high quality lawn tops for golf course fairways and the like, they must be mowed about 2-3 times per week during the high temperature growth season, and in some cases growth retardants are dispersed on purpose to reduce the mowing frequency. This leads to a notable increase in maintenance costs. The Manilagrass of the invention also provides an improvement in this respect.
It is an object of the present invention to provide a new variety of Manilagrass that retains its green leaves in winter while containing substantially no anthocyanins throughout the year, as well as dwarfed Manilagrass, Manilagrass that has a high stolon density, and Eragrostoideae plant incorporating genotypes of the Manilagrass newly developed according to the invention.
For the purpose of the present invention, the term xe2x80x9cwinterxe2x80x9d will refer to the low temperature period in which conventional Manilagrass, which is the starting material for the invention, experiences loss of green leaves and undergoes coloration to brown or dried grass color under common practical outdoor cultivating conditions, and for example, Tottori Z. matrella at the research field of Kaisui Chemical Industry Co., Ltd. experiences withered leaf in early January, becoming dried grass colored across the entire covered region.
The mean measured temperature of a period of ten days for early January, 1999 was 6.6xc2x0 C., with a low temperature of xe2x88x920.8xc2x0 C. Table 1 shows the weather conditions from mid December, 1998 to early March, 1999 at the above-mentioned research field.
Considering the different temperature fluctuation patterns in different years, winter was defined as conditions where the mean temperature of a period of ten days is around 6xc2x0 C. or below and the lowest temperature of this period is xe2x88x921xc2x0 C. or below. Since the lower temperature limit could not be evaluated in the field experiment, a hardening test was conducted as in Example 3 and FIG. 12, and the lower temperature limit was found to be xe2x88x9215xc2x0 C.
xe2x80x9cMaintaining green leavesxe2x80x9d means maintaining a green to yellow-green color without turning brown or dried grass colored or undergoing change to purplish red, dark green-purple or blackish-purple color even in the few remaining living leaves during winter, as occurs with conventional Manilagrass, and clearly maintaining a condition recognized as xe2x80x9cgreenxe2x80x9d across the entire covered region.
According to the invention, xe2x80x9cthroughout the yearxe2x80x9d means that the varieties of the invention maintain green to yellow-green stems, leaves and spikes throughout the year in periods and regions in which conventional Manilagrass contains anthocyanins in the stems, leaves or spikes depending on the season and undergoes coloration to purplish red, dark green-purple or blackish-purple, and xe2x80x9ccontaining substantially no anthocyaninsxe2x80x9d means not only that no purplish red, dark green-purple or blackish-purple coloration is visually found on the ground areas, but also that anthocyanins are absent (undetectable) or present in only trace amounts based on analysis results for the season and plant parts in which conventional Manilagrass undergoes coloration due to anthocyanins, as explained in the examples given below.
According to the invention, the xe2x80x9cimmature internodes of the front part of the main stolonxe2x80x9d are the section in which the internodes, at the front part of the main stolon including the shoot apex, is still undergoing vegetative growth.
A xe2x80x9cparental strainxe2x80x9d according to the invention means a strain used as the starting material for crossbreeding, mutation, cell fusion or gene introduction.
As mentioned above, turfgrass has been subjected to seeding methods for the purpose of increasing green color in winter, and has been used for attempted crossbreeding to shorten the dormant period. However, the results obtained by such methods have not satisfied the market need.
All conventional Manilagrass, to a widely varying degree depending on the cultivating region and variety line, experiences withered leaf and browning during winter with reduction in chlorophyll in the barely living sections, while anthocyanins also accumulate in large amounts, such that blackish-purple coloration occurs. Thus, in order to improve the greenness in winter it is necessary to increase the living leaves or inhibit decomposition of chlorophyll while inhibiting production of anthocyanins, while it is also necessary to minimize freezing of living leaves by frost and prevent any notable chlorosis (decomposition of chlorophyll); high wear resistance is also preferred for low temperature growth stagnation periods, but no Manilagrass obtained by conventional methods has yet exhibited the properties that are the object of the present invention. According to the invention, the line having gene mutation inducing novel genotypes, characterized by maintaining green leaves during winter, preventing accumulation of anthocyanin, and having properties described in claims 2-3, which are not found in the parental strain and any other conventional Manilagrass by genetically mutating manipulation on the parental strain, was successfully created.
The Manilagrass of the invention thus contains well-defined purposive conversion induced in the parental strain line, by a series of independent technical systems including a combination of mutation methods such as cellular mutation, ultraviolet irradiation, X-ray irradiation or the like, formation and use of a kind of shoot primordia and selection of transmutated cells as a process for creating a transmutated variety with a direction toward the prescribed goal. The invention has created completely new genotypes that retain the features of Manilagrass such as a narrow blade width and resistance to frozen withered leaf due to frost, while also: (1) retaining green leaves at low temperature even though it is Manilagrass, (2) containing substantially no anthocyanins, (3) having a short internode length, and (4) having high lateral stolon growth; this has been achieved without relying on conventional methods such as natural hybridization, artificial crossbreeding, cell fusion, gene introduction or selection of wild varieties. These genotypes are fixed and are not genotypes obtained by transfer or introduction from other varieties but rather are completely new Manilagrass genotypes. The scope of the invention therefore encompasses Eragrostoideae plant with the features of the invention, obtained by adding further mutation using the variety of the invention, by introducing other genes therein, or by using conventional methods such as crossbreeding for introduction of the new genotypes of the variety.